Phosphors are used in mercury vapor discharge lamps and viewing screens of various electronic devices. It has been recognized that various improvements in the performance of phosphors can be obtained if the phosphor material is coated with a protective film or pigment. Such coatings have been applied, for example, by using selective additions to a lamp coating suspension, or by suspending particles of the phosphor in a solution containing the coating material and evaporating the solvent to form coated phosphor particles.
One method, described in U.S. Pat. No. 4,585,673 to Sigai, the teachings of which are hereby incorporated by reference, involves the formation of a continuous coating by gas-phase chemical vapor deposition of the coating material on the phosphor particles while the particles are suspended in a fluidized bed.
U.S. patent application Ser. No. 07/430,546, now abandoned, copending and commonly assigned to the assignee of the instant application, entitled "Method for Coating Phosphor Particles" to Munn et al., the teachings of which are hereby incorporated by reference, describes a method for applying a coating to phosphor particles.